Shear Failure of Rock Under Compression

1965 ◽  
Vol 5 (02) ◽  
pp. 167-176 ◽  
Author(s):  
William C. Maurer
Keyword(s):  
Shear Strength ◽  
Failure Mechanism ◽  
Shear Failure ◽  
Heterogeneous Material ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Axial Pressure ◽  
New Concepts ◽  
External Pressures ◽  
Inclined Planes

Introduction It is difficult to produce tensile stresses under the high compressive stresses present in the earth; therefore, in deep drilling and geological faulting, shear failure predominates. This shear failure mechanism is complicated because rock is a heterogeneous material containing pore spaces, microfractures, elastic discontinuities and other imperfections. A study of shear failure of rock under pressure has been made to obtain a better understanding of this complex mechanism. A machine has been developed and used to measure the shear strength of rock and friction along sheared surfaces. This machine has certain advantages over the compression test-shear properties can be measured under low normal stresses and shear stress and normal stress can be varied independently. The first part of this paper is a description of shear failure of rock under pressure. The role of shear strength and friction along fracture surfaces in the shear failure mechanism will be discussed. The second part consists of a description of the shear machine and a discussion of the shear strength and friction data obtained using this machine. It will be shown that shear strength depends upon the size of the stressed zone, and that friction does not increase linearly with contact pressure as usually assumed. Attempts are made to relate some of the new concepts to tectonic failure and to drilling. SHEAR FAILURE IN ROCK TRIAXIAL TESTS The shear failure mechanism is illustrated by the triaxial test shown in Fig. 1. In this test, a cylindrical rock specimen is subjected to a confining pressure, pc, and an axial pressure, pa. These external pressures produce normal o and shear r stresses on inclined planes within the specimen equal to (1) (2) where theta is the angle between the specimen axis and a normal to the inclined plane. Fig. 2 shows how triaxial specimens deform as the axial pressure is increased. SPEJ P. 167ˆ

A Change of Undrain Shear Strength of Soft Ground during Consolidation Process

2014 ◽  
Vol 513-517 ◽  
pp. 269-272
Author(s):  
Yeong Mog Park ◽  
Ik Joo Um ◽  
Norihiko Miura ◽  
Seung Cheol Baek
Keyword(s):  
Shear Strength ◽  
Soft Clay ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Test Results ◽  
Exponential Equation ◽  
Consolidation Process ◽  
Degree Of Consolidation ◽  
Clay Ground ◽  
Strength Increment

The purpose of this study is to investigate the undrain shear strength increment during consolidation process of soft clayey soils. Thirty kinds of laboratory triaxial tests have been performed using undisturbed and remolded Ariake clay samples with different degree of consolidation and 5 kinds of confining pressure. Test results show that well known linear equation proposed by Yamanouchi et al.(1982) is overestimated the strength of undisturbed soft clay ground in the process of consolidation. A new simple and reasonable exponential equation proposed in this paper.

scholarly journals Effect of Geotextile Reinforcement on Shear Strength of Sandy Soil: Laboratory Study

2016 ◽  
Vol 38 (4) ◽  
pp. 3-13 ◽  
Author(s):  
Sidali Denine ◽  
Noureddine Della ◽  
Muhammed Rawaz Dlawar ◽  
Feia Sadok ◽  
Jean Canou ◽  
...  
Keyword(s):  
Shear Strength ◽  
Mechanical Behaviour ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Loose Sand ◽  
Test Results ◽  
Compression Tests ◽  
Confining Stress ◽  
Natural Sand ◽  
Confining Pressures

Abstract This paper presents results of a series of undrained monotonic compression tests on loose sand reinforced with geotextile mainly to study the effect of confining stress on the mechanical behaviour of geotextile reinforced sand. The triaxial tests were performed on reconstituted specimens of dry natural sand prepared at loose relative density (Dr = 30%) with and without geotextile layers and consolidated to three levels of confining pressures 50, 100 and 200 kPa, where different numbers and different arrangements of reinforcement layers were placed at different heights of the specimens (0, 1 and 2 layers). The behaviour of test specimens was presented and discussed. Test results showed that geotextile inclusion improves the mechanical behaviour of sand, a significant increase in the shear strength and cohesion value is obtained by adding up layers of reinforcement. Also, the results indicate that the strength ratio is more pronounced for samples which were subjected to low value of confining pressure. The obtained results reveal that high value of confining pressure can restrict the sand shear dilatancy and the more effect of reinforcement efficiently.

scholarly journals Studying Shear Performance of Flax Fiber-Reinforced Clay by Triaxial Test

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Qiang Ma ◽  
Yicong Yang ◽  
Henglin Xiao ◽  
Wenwen Xing
Keyword(s):  
Shear Strength ◽  
Triaxial Test ◽  
Confining Pressure ◽  
Fiber Content ◽  
Flax Fiber ◽  
Triaxial Tests ◽  
Fiber Reinforced ◽  
Shear Performance ◽  
Strain Relationship ◽  
Reinforced Clay

Laboratory triaxial tests were carried out to investigate the reinforcement mechanism, to study the characteristics of flax fiber-reinforced clay, and to discuss the effect on stress-strain relationship and shear strength parameters of flax fiber-reinforced clay in different flax fiber content and different confining pressure. Respectively, the ratio of fiber content to clay by weight is 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%, and the confining pressure is 100 kPa, 200 kPa, and 300 kPa in triaxial test. The test results show that, the shear strength of flax fiber-reinforced clay is greater than that of pure clay. Compared with the pure clay, the shear strength of flax fiber-reinforced clay increased as the cohesion and friction increased; while the increase of the friction is relatively small, the increase of cohesion is large. The shear strength firstly increased and then reduced with the increase of flax fiber content. When the fiber content was 0.8%, the shear strength reached a peak value, and the shear strength reduced with the further increase of fiber content.

scholarly journals The Influence of Segregation Size of Peat and Pre- Consolidation Pressure on the Effective Shear Strength Properties

2018 ◽  
Vol 250 ◽  
pp. 01013
Author(s):  
Norhaliza Wahab ◽  
Mohd Khaidir Abu Talib
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Peat Soil ◽  
Confining Pressure ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Consolidation Pressure ◽  
Sieve Size ◽  
Preconsolidation Pressure ◽  
Fiber Size

The degree of composition for peat soil in geotechnical engineering may affected the shear strength of the peat soil based on their types (sapric, hemic and fabric). The strength was affected by many factors such as its origin, water content, organic matter and arrangement of peat fibric. The aims of this paper was to investigate the influence of segregation peat sizes and preconsolidation pressure on the effective shear strength properties of reconstituted peat 1.000 mm (<RS1.00) and reconstituted peat 2.360 RS2.36). All the reconstituted peat samples were segregated through passing opening sieve size 1.00 mm and 2.36 mm with the aid of water to obtain homogeneous reconstituted peat slurry and were preconsolidated with 50 kPa, 80 kPa and 100 kPa pressure to obtain samples for triaxial tests. The Triaxial Consolidated Undrained Test was selected to test the shear strength properties of the reconstituted peat samples by using confining pressure 25 kPa, 50 kPa and 100 kPa. Both of the effective shear strength properties result such as cohesion and angle of friction obtained recorded <RS2.36 has higher strength than <RS1.00. The main factors that contribute to the differences shear strength value between two size reconstituted peats were segregation of peat size which affected by peat size (fiber size) and also pre-consolidation pressure applied which reduced the voids, water content and also improved the stiffness and strength of the specimen. All specimen and testing was conducted at RECESS, UTHM.

Experimental Study on the In Situ Mechanical Properties of Methane Hydrate-Bearing Sediments

2013 ◽  
Vol 275-277 ◽  
pp. 326-331 ◽  
Author(s):  
Zhong Ming Sun ◽  
Jian Zhang ◽  
Chang Ling Liu ◽  
Shi Jun Zhao ◽  
Yu Guang Ye
Keyword(s):  
Shear Strength ◽  
Methane Hydrate ◽  
Failure Time ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Hydrate Saturation ◽  
Confining Pressures ◽  
Coulomb Failure Criterion ◽  
Hydrate Bearing Sediments

TDR was introduced to solve the problem of how to measure hydrate saturation accurately. Then a series of un-drained triaxial tests were carried out on methane hydrate-bearing sediments under various conditions with effective confining pressures at 1, 2 and 4 MPa, average hydrate saturations at 15.71, 35.7 and 56.49% and strain rate at 0.8%/min. The results indicate that the shear strength increases with the increases of effective confining pressure and hydrate saturation, but the maximum failure time decreases with the increasing effective confining pressures. According to Mohr-Coulomb failure criterion, the shear strength of methane hydrate-bearing sediments was analyzed. It can be found that the internal friction angles are not sensitive to hydrate saturation, but the cohesion shows a high hydrate saturation dependency.

Effect of roughness on shear behavior of red clay – concrete interface in large-scale direct shear tests

2015 ◽  
Vol 52 (8) ◽  
pp. 1122-1135 ◽  
Author(s):  
Xiaobin Chen ◽  
Jiasheng Zhang ◽  
Yuanjie Xiao ◽  
Jian Li
Keyword(s):  
Surface Roughness ◽  
Shear Strength ◽  
Large Scale ◽  
Shear Failure ◽  
Friction Angle ◽  
Confining Pressure ◽  
Shear Behavior ◽  
Interfacial Shear ◽  
Red Clay ◽  
Direct Shear Tests

Few studies have focused on evaluating regular surface roughness and its effect on interfacial shear behavior of the red clay – concrete interface. This paper presents the results of a series of laboratory large-scale direct shear tests conducted using different types of red clay – concrete interfaces. The objective is to examine the effect of surface roughness on these types of soil–concrete interfaces. In the smooth-interface tests, the measured peak and residual shear strength values are very close to each other, with no observed shear dilation. The surface roughness is found to have a remarkable effect on the interfacial shear strength and shear behavior, with the shear strength increasing with increased surface roughness level. The shear dilation is likely to occur on rougher interfaces under lower confining pressure due to the behavior of compressed clay matrices. Owing to the clay matrix’s cohesion and friction, the interfacial shear strength on rough interfaces consists of cohesive and frictional forces between the clay and concrete surfaces. The friction angle value is observed to fluctuate between the clay’s friction angle and the smooth interface’s friction angle. This can be related to the position change of the shear failure slip plane. The confining pressure and surface roughness could change the shear failure plane’s position on the interface. Furthermore, the red clay – structure interface is usually known as the weakest part in the mechanical safety assessment.

scholarly journals Investigation of Separation Non-Persistent Faults in Fracture Mechanism of Rock Bridge

2016 ◽  
Vol 2 (7) ◽  
pp. 348-357 ◽  
Author(s):  
Nasim Nohekhan Hokmabadi ◽  
Vahab Sarfarazi ◽  
Mohamadreza Moshrefifar
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Heterogeneous Material ◽  
Failure Pattern ◽  
Test Machine ◽  
Shear Load ◽  
Horizontal Edge ◽  
Rock Bridge ◽  
Uniaxial Test ◽  
Two Sides

Rock mass is a heterogeneous material included joints, fractures and faults. The necessity of rock mechanics studies in conducting constructional issues has become important due to the increase in constructional works and the expansion of the structure’s dimension and especially creating underground spaces in rock masses. Faults are the most important discontinuous fractures in the earth's crust in which the two sides of the fracture have moved relative to each other. The purpose of this research is that if the non-persistent faults were situated adjacent to each other, how would be the shear failure mechanism of Rock Bridge surrounded between the faults. For this purpose, physical model consisting two horizontal edge faults and a surrounded angled fault was built; angularity of the central fault varies from 0° to 60° with increasing the 30°. The central fault places in 3 different positions. Along the lateral faults, 1.5 cm vertically far from the edge faults and 3 cm vertically far from the edge faults. All samples tested by uniaxial test machine so that shear load was distributed in the specimens due to special geometry of specimen. The results show that the failure pattern was mostly influenced by configuration of central joint, while the shear strength was linked to the failure pattern and failure mechanism.

scholarly journals Statistical evaluation of shear strength parameters of fine grained tills

2021 ◽  
Author(s):  
Chandra Prakash Poudyal
Keyword(s):  
Shear Strength ◽  
Stress Ratio ◽  
Maximum Stress ◽  
Shear Failure ◽  
Triaxial Tests ◽  
Ratio Method ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Fine Grained ◽  
Deviator Stress

A statistical analysis is conducted in this study on the shear strength parameters of fine-grained tills from a series of consolidated undrained triaxial tests performed for a light rail transit project in the City of Toronto. Three different failure criteria are applied: the maximum stress ratio, the maximum deviator stress, and the residual stress. Three methods generate only minimal difference in the shear failure angle and a slight difference in cohesion. The friction angle calculated using the maximum stress ratio method ranges from 18.6 to 35.26 degrees compared with values ranging from 18.5 to 34.26 degrees by the maximum deviator stress method. The undrained shear modulus calculated from one-third and two-third peak deviator stress points generate a wide variation from 2 MPa to 167 MPa with an average value of 34 MPa.

scholarly journals Shear Properties of Asphalt Mixtures under Triaxial Compression

2019 ◽  
Vol 9 (7) ◽  
pp. 1489 ◽  
Author(s):  
Tuo Huang ◽  
Shuai Qi ◽  
Hongfu Liu ◽  
Huanan Yu ◽  
Sheng Li
Keyword(s):  
Shear Strength ◽  
Asphalt Pavement ◽  
Asphalt Mixture ◽  
Friction Angle ◽  
Confining Pressure ◽  
Asphalt Mixtures ◽  
Triaxial Tests ◽  
Cohesion Strength ◽  
Failure Envelope ◽  
Shear Properties

In order to study the influences of confining pressure and temperature on the shear properties of asphalt mixtures, triaxial tests were conducted at 40 °C, 50 °C, and 60 °C, with the confining pressure ranges from 0 to 1 MPa for the widely used continuous-graded AC (Asphalt Concrete)-13, open-graded OGFC (Open-Graded Friction Course)-13, and gap-graded SMA (Stone Mastic Asphalt)-13 asphalt mixtures in China. A nonlinear regression/prediction model of triaxial strength for asphalt mixtures was proposed. The results show that confining pressure and temperature had a significant effect on the shear resistance of asphalt mixtures. With increasing temperature, the shear strength of the asphalt mixture gradually decreased due to the decreasing of cohesion strength; the shear strength of the asphalt mixture increased with the increase of confining pressure. Meanwhile, the cohesion strength increased and the friction angle decreased gradually with the increase of confining pressure. When the confining pressure was close to 0.6 MPa, the Mohr–Coulomb failure envelope bended down, so the linear Mohr–Coulomb criterion is not suitable to describe the failure behavior of asphalt mixtures. Therefore, a power function failure envelope was put forward to characterize the nonlinear shear properties of asphalt mixtures. The nonlinear evolutional laws of shear parameters, which includes cohesion strength and friction angle, were also proposed for asphalt pavement material and structure design. Among these asphalt mixtures, the gap-graded SMA-13 asphalt mixture exhibited better performance on the resistance to shear failure, and it was recommended as the upper layer material to improve the shear performance of asphalt pavement.

Research on Shear Failure Criterion for Layered Rock Mass

2012 ◽  
Vol 446-449 ◽  
pp. 1491-1496 ◽  
Author(s):  
Zhi Zeng Zhang ◽  
Lan Lan Zhou ◽  
Zhen Xia Yuan ◽  
Zhong Hua Sun
Keyword(s):  
Rock Mass ◽  
Failure Criterion ◽  
Shear Failure ◽  
Three Dimensional ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Layered Rock ◽  
Layered Rock Mass ◽  
The Stability ◽  
Confining Pressure Effect

In order to study the stability of layered rock mass, a shear failure criterion for layered rock mass is presented and its program is compiled in C language. The shear failure criterion consists of two parts: firstly, four empirical expressions are suggested in which shear strength parameters vary with the direction; secondly, a pilot calculation method is developed to judge whether a shear failure plane in layered rock mass occurs or not and give its occurrence under three dimensional stress condition. A triaxial numerical experiment on layered rock mass is designed to test the shear failure criterion, and its results reflect the characters including obliquity effect, confining pressure effect and failure mode which conform to the previous triaxial tests.

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